Back then...this is what we did...

[absolom7691]

This thread and Greg's cycloid generator thread have been an absolute joy to read. This pioneering tech and the pros that performed on this equipment still inspires. Thank you for sharing, everyone!

[lasermaster1977]

Ahh.. I see (said the blind man). Are ILDA standards for +/- differential RGB signals still a thing, for noise suppression on long cable runs, but only the + side is used on the LD driver board's inputs, with common grounds for RGB?
Thanks again for the hand-holding, guys. I'm getting there, but still playing ketchup.

The diff +/- inputs for XY and RGB are there primarily to maximize noise suppression. For 0-5v RGB analog or TTL signals, their grounds connect to the RGB - terminals. LD driver board inputs vs ILDA, six of one, half a dozen of another.

[TheHermit]

The diff +/- inputs for XY and RGB are there primarily to maximize noise suppression. For 0-5v RGB analog or TTL signals, their grounds connect to the RGB - terminals. LD driver board inputs vs ILDA, six of one, half a dozen of another.

Thanks for the reply. That's pretty much what I was assuming. Still debating whether it would be worth including differential outputs on my correction amps for ILDA compliance, before putting the final nail in that coffin.
Is line noise even still an issue in today's pro world of long Ethernet runs to local ILDA DACs, daisy chained banks, and onboard FB4s?🤔

[lasermaster1977]

Thanks for the reply. That's pretty much what I was assuming. Still debating whether it would be worth including differential outputs on my correction amps for ILDA compliance, before putting the final nail in that coffin.
Is line noise even still an issue in today's pro world of long Ethernet runs to local ILDA DACs, daisy chained banks, and onboard FB4s?🤔

IMHO, not worth it for RGB control lines if the XY & RGB signals between your DIY host image controller/generator and the ILDA projector DB-25 input is less than 10-20 feet or thereabouts, TTL is already fairly noise immune, but I prefer to keep the XY outputs to the ILDA projector's XY inputs differential.

If your using Ethernet runs to ILDA DACs then XY & RGB signals are already being handled as differential pairs. That's my bet and I stickin' to it.

[TheHermit]

IMHO, not worth it for RGB control lines if the XY & RGB signals between your DIY host image controller/generator and the ILDA projector DB-25 input is less than 10-20 feet or thereabouts, TTL is already fairly noise immune,

Personally, I'm only running ~20ft of USB to my 'ILDA DAC(s)', then ~10ft of DB25 ILDA (printer) cable to the projector. But, for the convenience of others, I'm concerned with ILDA compliance, because that's the standard interface for everyone's projectors. You know me, the idealist.
My paw used to say, "If ya do things right the first time, then you'll never have to do it again."

but I prefer to keep the XY outputs to the ILDA projector's XY inputs differential.

LOL! That's where I was 2 weeks ago, before having these conversations about using the single sided, bipolar OPA188.

If your using Ethernet runs to ILDA DACs then XY & RGB signals are already being handled as differential pairs. That's my bet and I stickin' to it.

Darn tootin', Partner. Now yer talkin' and that goes double for me.
😎

[lasermaster1977]

Cool, feels right to me.
I tried to use the OPA188s, but couldn't find any circuit examples in documentation that seemed to apply to my application. So, I thought, "There are + & - inputs and an output, just like an op amp. The example circuits (that I don't understand) have circuits with feedback resistors, so why not hook it up to a 2k input resistor and a 10k trim pot and see whether it works or makes magic smoke." Neither happened. It only produced an asymmetrical, flattened sine wave with an offset 🤔 and the feedback pot didn't do anything.
While waiting for the OPA188s to arrive, I had successfully tested a TL084 -5v/+5v p-p differential X/Y circuit, as well as a 0-5V p-p RGB circuit. Following @Laserist's advice, I've increased the input resistors from 1k to 2k, then optimized the values of the offset pots.
Here's my kicad schematic:
T4 Laser Synth ILDA conversion schematic
Of course, it's still a work in progress and I still need to add the power, caps, PT8211 DAC, & T4.1. But, it shows what we've been discussing (I hope).

If Lasermaster1977 and Laserist wouldn't mind having a gander, your feedback would be most appreciated, before I get too far down a potentially dead end road.
Thanks guys.
😎

With TL084 and the like, I'd recommend keeping the - input resistor to a minimum of 5K, 10K being common, while Rf, the feedback resistor can be smaller for a gain smaller than 1 or 10K for gain of 1, or larger for a gain > 1. The + input would be grounded, or a value = to the parallel resistance of Rin and Rf.

I'll take a quick gander then edit this reply. [Edit] I'd do it slightly different, although yours would probably work.
Eliminate have the offset voltage divider on the + input and instead put it on the - input with the other signal. To do this, feed the offset adjusting pot with -9v instead of +9v. Feeding a negative voltage into the inverting input...guess what...it inverts the offset polarity to be positive...the very thing you want. Then just ground the + input of the op-amp.

Having a 1:5 ratio for the offset pot and the input resistor will be slightly non-linear over the range of adjustment of the pot. The input resistor tied to the pot is essentially in parallel to the pot's wiper position's resistance value to Gnd. This is because both op-amp's input terminals are "virtual grounds" themselves.

Doing this will greatly simply your circuitry because all +inputs of the op-amps would now be tied to Gnd.

I just thought of something, that I hadn't paid much attention to, my bad. My above comment is based on your using + and - 9v to power the op-amps. I'll look at your schematic again and get back to you.

[2nd Edit]
1. What are the inputs to R11 and R12, e.g. voltage amplitude range and polarities, I'm guess they are the XY signals being converted to differential for ILDA, right?
2. Is the DB-25 connector is the ILDA output connector, right ?
3. Are the 2 pairs of HP_R and HP_L signals equating to RGB blanking?
4. I'll sketch up a schematic showing when I get these answers.

[lasermaster1977]

✔I'll bump up Ri to 5k. @2k, Rf is 7k for a gain, of ~1 3/4 (0/+3V to -5/+5V)

That was my original thinking, but 'monkey see, monkey do'.
Thanks. ;-)


Roger that. ;-)

Love to KISS.

Yes, I'm powering the rails with +9/-9V. This is exactly what I needed to know, Lasermaster1977. Here, I was all proud of making a purdy picture and would have never known any better. Worked ok during the tests.🤷*♂️
Very cool of you to take the time.
😎

What you did worked, as you said, but could be improved this way:

[laserist]

I looked up the sgtl5000xnaa3 on your schematic and Mouser has it listed as end of life. I'd go at least 10k on the op-amp's. You need to take into account any signal fan out of the outputs. Laserium just kept hooking things up to more and more places. The current draw adds up quick. There's a virtual ground for the headphone outputs that might be superior to manually offsetting the signal. The manual offset will move if your voltage drifts. I'm old school could you explain why a codex is the right chip?

[mixedgas]

One of these three lovely PDFs contains everything you would want to know about the origional ILDA TX-RX circuits including the single / double ended receiver with switch selection. Even specs the cable impedance and drive levels are well defined.

ALL MODERN galvo amps use differential inputs. Some of them are pretty crappy driven single ended, because of well, board layout.

ILDA STANDARDS (photonlexicon.com)

Steve

[lasermaster1977]

I've been doing some invigorating stuff since this past May, at least it has been fun and rewarding. But, it all started over three years ago in April 2019 when an old competitor of mine, and probably known by many of you older laser folks, reached out to Buffo, who was then referred to Icecruncher, who then reached out to me. The old "back then this is what we did" kind of guy, wanted his Apple II laser images converted to a newer format that he could use with QuickShow. Icecruncher asked if I'd be interested in working on converting these old images to the appropriate IDLA format. I said, heck yea. For now, I will respect his privacy by not mentioning his name and make the choice his to come forward. He is on the PLF forum but has a lot on his hands right now.

Icecruncher created disk images from the old Apple DOS3.3 double-sided floppy disks and sent them to me this past May. Off and on during the intervening time I looked at, reviewed and became familiar with this Apple IIe software that included binary DAC drivers, binary laser images and Floating-Point Basic programs for image creation, editing, and program animation preparations. Once I was familiar enough with it all, I began designing and coding Apple II base software for reading in blocks of image files from the digitized disk images and converting them from their native format to the ILDA Type 5 RGB format. There were just over 2,700 images that were to be converted so coming up with an time efficient way with doing them all in the shortest amount of time was forefront on my mind. And, there were there different image byte-size formats, some that were created before any of us had "blanking" capability or color defining capability built-in to the image data, and later image formats that had RGB data for every point in an image.

I wanted this to be done using the native Apple II/II+/IIe programming methods but with a slight, but significant uptick in technology by using an Apple II emulator and a disk image/file tool for Windows, known as the AppleWin emulator and CiderPress respectively.

By the first week of this October I had proven my conversion methodology worked and produced the first half-dozen image conversions to an .ild Windows PC binary file format and successfully imported these .ild files into my FB3/QuickShow. The 2nd week of October I finalized the Apple II FP Basic conversion software that allowed me to enter a specified number of image names that were on a corresponding image disk in the AppleWin emulators Disk 2, type in the image names and when the nth image was finally entered the program sequentially loaded each image, plotted the image in Apple IIe's HiRes graphics window while converting the point data and building an ILDA formatted binary image, with ILDA Header/Footer, filename, point-count and RGB data for each image point into a separate memory buffer, save the ILDA binary file to a separate mostly empty disk image in Drive 1.

The next steps were reading the disk image that contained the ILDA binaries with CiderPress and exporting the all the selected files in bulk to a PC binary file format and into a Windows folder. The first 30 or so image conversions were done at the Apple II's original yet emulated clock speed of 1 MHz just to ensure that it all went right on a consistent basis. It took 60 seconds to convert a 512 byte image to an ILDA RGB equivalent file format or 63 seconds if the image was plotted on the screen during conversion. I could see that at 1 MHz CPU clock speed this was going to take weeks and weeks and weeks. But wait...

Then...the AppleWin emulator's virtual CPU clock speed was increased by a factor of 645 times to 645 MHz. The result was the ability to convert 14-40 images (depending on the original images point count) in about 2 seconds for around 40 256 point images, to 4-5 seconds for around 14 to 20 400-1023 point images, and each image was plotted on the emulated Apple IIe's HiRes screen in the process. flash..flash..flash..blink..blink..blink..done.

Working only in the evenings 3-4 hours, I converted all 2,761 in about 7 days.

The .ild imported files into QuickShow looked amazing when displayed on the QS screen and when scanned by a 20K RGB projector. Given QS's enhanced abilities for frame editing/animation and show/effects compiling, I was quite impressed with the results.

This individual now has, not only a better disk archive of his precious Apple II floppies, now in the form of PC readable digital disk images, but his 2,761 images in an importable, binary ILDA image format.

(Last night I started on adapting my conversion software to handle my original Apple II/IIe laser image formats.)

Don't get me wrong. I am still amazed and attached to the extended capabilities of the 1 or 2 MHz Apple IIe or IIgs for doing laser graphics (abstract or otherwise), animations and beam shows, yet it is nice to see old images come alive within today's newer technology.

Cheers,

https://youtu.be/tSe4SZvRUbU


Edit Update: I finished the ILDA image conversion software adaptation to convert my original, various XY image formats (no blanking, with on/off blanking and on/off RGB blanking). I also had 2,761 images across about 100 5-1/4" floppy disks in all, including duplicates of the same image. 260 of those are RGB images made between 2017 and 2020 by modifying earlier images or creation of new ones. About half of these "images" are abstract geometric images.